About 166.5 million Americans wear prescription glasses. Each person who wears corrective lenses has a prescription chart that describes their lens power and type. Your eyeglass prescription might look confusing at first glance - it's an assortment of abbreviations and numbers that can seem perplexing.

So, how can you make sense of this information?

Key Takeaways

• Abbreviations like OD, OS, and OU describe either or both eyes.
• Values for SPH describe the overall correction needed for nearsightedness or farsightedness.
• CYL and Axis values pertain to astigmatism correction.
• A minus (-) number indicates nearsightedness, while a plus (+) number indicates farsightedness. The higher the value, the stronger the lens prescription.

Keep reading, and we'll tell you how to decipher your eyeglass prescription.

See Related: How Far Can The Human Eye See?

Your Glasses Prescription, Explained

You've booked an appointment at your eye clinic, and you're ready to improve your eyesight. At your visit, your optometrist will perform a comprehensive eye exam to ensure your ocular health is in peak condition. And by the end, you'll return home with a gorgeous pair of hand-crafted luxury eyeglasses and a newfound sense of confidence!

All in all, visiting your eye doctor can be an enjoyable experience. However, you might feel a twinge of confusion when you look at your updated eyeglass prescription. What do all these numbers mean?

No, this assortment of abbreviations isn't Egyptian hieroglyphics. These numbers, like 20/20 or 20/10, simply describe the type and strength of lenses you need to see clearly. Luckily, it's much easier to decipher than it seems!

Keep reading, and we'll let you know how to read your eyeglass prescription.

Eyeglass Prescription Abbreviations

You'll likely see a variety of abbreviations when looking at your eyeglass prescription.

OD vs. OS vs. OU

• OD or RE: Your right eye. OD is an abbreviation for the Latin term oculus dexter, which means "right eye." The abbreviation RE is sometimes used instead.
• OS or LE: Your left eye. OS is short for the Latin term oculus sinister, which means "left eye." The abbreviation LE is sometimes used instead.
• OU: Both of your eyes. OU stands for oculus uterque, which means "both eyes" in Latin. However, this isn't commonly used, as most people have a different strength prescription for each eye.
• NV: Your near-vision prescription.
• DV: Your distance-vision prescription.
• PD: Your pupillary distance. This measures the space between your pupils and is important when centering eyeglass lenses. An accurate reading will ensure you have the most precise vision.

You will likely see other abbreviations on your prescription chart, such as SPH and CYL.

Bonus: How To Remove Scratches From Glasses

Sphere (SPH)

Most people's eyes are round and have a slight curvature. SPH, or Sphere, indicates that the overall correction is spherical and equal in all meridians of the eye. SPH describes the amount of lens power needed to correct nearsightedness or farsightedness. A minus (-) number means you are nearsighted, while a plus (+) means you are farsighted.

Cylinder (CYL)

About one in three Americans have astigmatism, meaning their cornea is not spherical. CYL, or Cylinder, describes the amount of lens power needed to correct astigmatism. A minus (-) number signifies you have a nearsighted astigmatism, while a plus (+) means you have a farsighted astigmatism.

For those with astigmatism, there is no universal fix available. Your optometrist will likely use both CYL and SPH measurements to account for the differences in your eye's curvature. If you have no number shown in your chart under CYL, that means you either have no or negligent astigmatism.

Axis

Axis is another prescription value that pertains to astigmatism. If your chart has a CYL (cylinder power) value, then it will also have an Axis value.

The human eye is oblong-shaped, similar to that of a football. Because of this, there are two different curvatures of the eye.

Axis indicates where the astigmatism is on your cornea. It describes the tilt of your eye on a scale of 0° to 180°. A value of 90° lies on the vertical meridian of the eye, while a value of 180° lies on the horizontal meridian. People with astigmatism typically have two main curvatures roughly 90° apart.

Add

Bifocals and progressives are lens types that feature more than one prescription. Add is the added magnifying power applied to the bottom portion of your lenses for multifocal prescriptions.

Prism

If you have double vision (diplopia), you may require prism correction. Double vision is a refractive error that occurs when the light entering your eye hits two areas of the retina instead of one. A prism correction on your eyeglasses will bend the light entering the eye so it hits one area.

The location of your prismatic correction can be described with the following abbreviations:

• BU: Base up.
• BD: Base down.
• BI: Base in.
• BO: Base out.

Eyeglass Prescription Numbers

Your optometrist will describe the strength of lenses you need using diopters. A diopter (dpt) is a unit of measurement that expresses the optical power of a prescription lens. Eyesight can be described using either plus (+) or minus (-) numbers. A score of 0 diopters means that you do not require any eyesight assistance from eyeglasses or contacts.

Though there are outliers, most prescriptions lie between -5 and +3 diopters.

A minus number means you have nearsightedness (myopia). A plus number means you have farsightedness (hyperopia). The larger the number, the stronger the prescription lens you need to see clearly.

Final Thoughts

With this newfound knowledge, you'll be familiar with the abbreviations and numbers on your prescription. Though you don't need to be well-versed in the ins and outs of eyeglass prescriptions, it may help you understand why you have the lenses you do!

Though you can't willingly choose your required lens power or prescription, you can choose the frames they sit in. Select a pair of designer frames from our curated collection of luxury eyewear and experience the difference that high-quality, featherlight, and effortlessly comfortable frames can make in your life!

Keep Reading: The Different Types of Glasses Lenses: A Guide To Lens Types

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Oculus Eyecare is Seattle’s premier optometry practice and optical boutique for those looking to see and be seen in a new way. Located in South Lake Union on Denny Way, Oculus Eyecare offers comprehensive eye care services and exams for individuals and families in Seattle. Click here to schedule an appointment or a personal styling session. To stay connected and learn more, follow us on Facebook, Instagram, and X/Twitter.